Gamma-(3-aminocyclohexyl)butyric acid and esters



GAMMA-(S-MVHNOCYCLOHEXYL) BUTYRIC AQID AND ESTERS Delaware No Drawing. Application September 7,1955 Serial No. 533,011

2 Claims. (Cl. 260--514) This invention relates to a process for the preparation of an aminoacid and its derivatives, to a linear polyamide made therefrom, and to processes for their preparation. The invention is more particularly directed to the manu facture of a linear polyamide characterized by properties having a high softening point and excellent thermostability.

Since the early fundamental research of Wallace H. Carothers and the issuance of his basic patents on condensation products from the diamines and dibasic acids and their subsequent polymerization, many studies have been made to produce resins having properties superior to those of the nylons already described in the literature, and to produce such polymers more cheaply. Caprolactam and other bifunctional compounds containing both amino and carboxyl groups have been studied. The instant invention concerns the last mentioned types of compounds, their preparation and their polymerization.

Inventa A.-G. fuer Forschung und Patentverwertung, in their Swiss Patent 276,924 of 1951, describe the preparation of resins from bicyclooctanoneoxime. The complicated and expensive process of the patent produces polymers having comparatively high melting points but the expense of their preparation, the brittleness of the polymers and the difliculty of fabricating the polymers into useful articles, markedly reduce the utility of such resins. The polymers of the patent contain this unit structure: 1. CHr-CH;

(-CO-OHrOH OH:NH)

CHr-C g The process of the instant application is directed to the preparation of a linear polyamide characterized principally by high softening point, good toughness, excellent thermal stability, and low melt viscosity at molding temperatures. Moreover, this superior polyamide is produced by a process which is much more economical than processes used for preparing resins having commensurate physical properties.

An object of the present invention is to provide a process for the preparation of a new polyamide together with intermediates for its preparation. A further object is to provide an aminoacid that can be homopolymerized to give orientable resins having excellent thermostability and low melt viscosity at molding temperatures. Yet another object is to provide an economical process for the preparation of the aforesaid intermediates and of the monomeric and polymeric compounds derived therefrom.

In accord with the invention, a linear polyamide of high softening point and excellent thermostability is obtained from a monomer having this structure:

11,0 on-cmcmcrnooon HIC on, \Q Him. in which R is hydrogen, ammonium, substituted ammo- Patent Eatented July 7, i959 Z nium, aliphatic or a cycloaliphatic group, and R is hydrogen or an alkyl. The aminoacid, gamma-(3-aminocyclohexyDbutyric acid, may be produced by a series of reactions illustrated by these equations:

J35 00 /CE 110 on ofi,\ A101, ofi (fi-GOOHHOHBOOOH an a t 0 CH CH on c-ooomcmcoon fuming as gift BNO;

on on -oocmomooon $5 on on CH o-ooomomooon Raneynickel (I: g 11 E H Ruo,

/C i mo cn-ornomomooon H CH1 f NH:

Reaction 3 may be conducted in accord with the well known processes of the art such as that described in Organic Synthesis, Coll., vol. II, p. 81. Reaction 4 may be conducted in accord with a customary nitration process such, for example, as those described in the Amblard et al. US. Patent 2,439,513. Reaction 5 is a catalytic hydrogenation reaction such as shown in the prior art with the exception that the nitrated derivative is first hydrogenated in a suitable solvent in the presence of a Raney nickel catalyst at a temperature between and 180 C. and a pressure of between 1500 and 7500 p.s.i. until an amount of hydrogen has been absorbed which corresponds roughly to reduction of the nitro and the carbonyl groups. The solvent is then removed by distillation. The solvent-free product of the hydrogenation is redissolved in aqueous sodium hydroxide and ruthenium dioxide is used to catalyze the second hydrogenation conducted under a temperature of -ll0 C. at l500-2000 p.s.i. hydrogen pressure, until hydrogen consumption stops (about two hours). During the hydrogenation reactions, the carbonyl group, benzene ring and N0 groups are converted, respectively, to methylene, cyclohexane and amine groups. The ammonium, substituted ammonium, aliphatic and cycloaliphatic R groups are produced by neutralization or esterification of the acid, or ester interchange of the esters.

The product of the aforesaid reactions as Well as the derivatives thereof, illustrated by the Formula 2, can be polymerized to a high softening polyamide having excellent thermostability by heating to a temperature between and 400 C., during which polymerization reaction the water, or other volatile material, formed by the combining groups of the polymer is withdrawn.

The examples which follow illustrate preferred embodiments of the invention in which parts'ereby weight unless otherwise indicated:

I. PREPARATION 6F INTERMEDIATES A; Betiz benz'oylpi'dpionic' acid A stirred suspension of 40lbs. of anhydrousaluminum chloride in 40 l. of benzene Washeated-t SO -C. and then 15 lbs. of succinic anhydride was added as rapidly as the evolution of hydrogen chloride would permit. After addition was'complete, heating under reflux was continued for anothertwohours. .The mixture"-was cooled and discharged onto a-large excessf ice, water and concentrated hydrochloric acid. The mixture stood overnight and then the excess benzene was stripped off under vacuum. The solid product was filtered off, washed with water and then dissolved in aqueous ammonia. The basic solution was warmed, treated with charcoaf and filtered. The filtrate was acidified'with'liydroclifori'c acid, the solid product filteredoif and washed with water. After drying thoroughly in air the product melted'at Ill-114 C. and weighed about 30 lbs. This is above the theoretical yield, but the product is pure enough for subsequent use.

B. Beta-(3-nitrobenz0yl)propionic acid Fuming nitric acid (90% HNO specific gravity 1.5, 10 lbs./ 1.5 lbs. of keto-acid) was cooled to 0 with stirring. The beta-benzoylpropionic acid was added in many small portions with continued stirring at a rate designed to keep the temperature below -10 C. '-S'tirring at the low temperature was continued for another two hours when the reaction mixture was poured into an excess" of ice and water. The precipitated solid was filtered off, washed with water and then recrystallized from glacial acetic acid and water.

i The yields from individual runs are tabulated below:

TABLE I Yield of Nitro Acid Amount of Beta-Benzoyl Pro- Melting pionic Acid 7 1 "Point, C.

Weight Percentage 44 164467 L." 42 161-164 39 161- 164 33 1162467 30 illie-164 v400 g 320g 37 ,;162166 9.0 lbs. 919 lbs 50 s 164465 Weight of starting material isgiven as snccinic antiydride'nn'd'ylcld is for two steps of Friedel-Crafts acylation and'nitration.

C. Gamma-(3-amin0cyclohexyl)'butyric ucid -A mixture'containing 25 g. of beta-(3 nitro benzoy1) propionic acid in a 150 ml. of a solvent, such as-' methanol, ethanol, propanol, and higher monohydroxy'aliphatic alcohols, was hydrogenated over g. of-R-aney nickel at about 500 atm. and 130135 C; (thepre'ss'ure-inay range, however, between 50 and 1000 atmsi -and the-temperature between 100 and 250 C.). Thecat"alyst;was then filtered off, the alcohol boiled off and the -i'e'Sidue dissolved in 150 ml. of 3% aqueous sodium hydroxide (or any suitable alkali or alkaline earth hydroxide) "and again reduced using 1-2 g. of rutheniurridioxid catalyst and hydrogen at 2000 p.s.i. and 100-110 C. Stip'eratmospheric pressures above 10 atmospheres and teniperatures between 75 C. and 150 C. may be'used. The catalyst was then removed by filtration a'ndth'e solution neutralized to pH-7 with hydrochloric'acid' The neutral solution was treated with charcoalfboiled "ahd filtered through Celite. After the filtrate was weueoneemrated it was diluted with dioxane to-precipitate=theproduct, which is recrystallized 'from'boiling water. Table H illustrates the efifectiveness of this reaction.

II. PREPARATTON OF POLY-GAMMA-(Zi-AMINO- vi CYCLOHEXYIJBUTRYIOACID "Dry monomeric gamma-(3-aminocyclohexyl)butyric 'acid' is placed in a-suitable receptacle, air and oxygen'removed either by evacuation with 'an oil pump or by replacementwith an-inertgas. A vesseL thus charged, and under a slow, steady stream of nitrogen, is plunged into a bathof boiling'vapors of hexachlorobenzene (B.P. 326

C.). The monomer melts very rapidly :down to a thin fluid liquid which froths,-loseswater vapor and becomes .thicker. After two hours, vacuum is, applied and heating continued at" the same temperaturefor another two hours. By this procedure polymers are obtained having -these properties:

PROPERTIES OF 'POLY-GAMMA-(ELAMINOOY CDOHEX YL) 'BUIYRIC ACID A.S.-'I.M.-

1157924-"... Density s g'I/cc. -#D69644 Thermal Coefficient of Linear 'Ex- "1190-3232(10 pension. Dielectric Constant (1,000 c.p.s.) Flexural Modulus at 23, C Flexural Modulus at C -Flefxural Strength {Tensile strength with Elongation of--.

Stress Relaxation Y Inherent Viscosity, 05%- solution in 70:30 mixture of phenol and 2,4,6- trichloro-phenol ln (relative viscosity) cone. in 3 100 ml.

1 The values are at room temperature. 1 Stress relaxation-82% retention after 63 hrs. at 73 F. at a strain of 0.0067 1'and at aniuitialstress of 2020 p.s.i. Sample ls'clamped in 'testifigfmachin'e and'elong'ated rapidly until a s'uitable'stfain is produced, the length is maintained constant and the force 4 formation -15 measured at-a series of-times. The stresses produced in the resultingirom the dcsgeclmen may be computed from thes'Tor'cs andthe dimensions of t e specimen.

' Moreover, the polyaniide is not affected in physical appearance by treatment with toluene," dioxane or chloro- 'form, although methanol and acetone give film a'slightly cloudy appearance.

- Esters of gamma-(3-aminocyclohexyl)butyric acid can be made by esterification of the acid with methyl, ethyl, nand isopropyl, nand isobutyL-and the higher molecular'weight' alcohols. Alternatively,- the esters may be made by'ester interchange of the'lower alkyl esters of the monomeric acid 'of the invention with-higher molecular weight alcohols-inthe presence ofa mild acid catalyst.

The polymers of the invention may be injection molded, extrusion molded or compression molded togive objects 'ofany desired shape; or contrariwise, may be formed, by other suitable processes, into filaments, bristles, films, and the like by extrusion. Films and sheets can likewise be prepared from solution casting of the polymers.

The monomers of the invention may be copolymerized with other monomeric polymerizable compounds and particularly with mixtures of other polyfunctional amines and polybasic acids heretofore employed for preparing CH3 H30 CH-CHa-CHg-CHzCOOR Hg CH1 1 NH:

wherein R is of the group consisting of hydrogen, methyl, ethyl, n-, and isopropyl, and n-, and isobutyl groups, and polymerizable to a linear polymer having a high softening point, an excellent thermal stability and a low melt viscosity at molding temperature, that has the repeating structural unit:

CHCHgCHzCH1CO- 2. In a process for the prepartion of gamma-(3- aminocyclohexyDbutyric acid by the hydrogenation of a beta-(3-nitro-benzoyl)propionic acid, the steps which 'comprise hydrogenating beta-(3-nitro-benzoyl)propionic acid in the presence of a monohydric alcohol and a Raney nickel catalyst, at a temperature between 100 and 250 C. under pressures between and 1,000 atmospheres, separating the catalysts and alcohol from the reaction product, neutralizing the resulting product with sodium hydroxide, and thereafter hydrogenating the neutralized product in the presence of ruthenium dioxide and at a temperature between and C. and at superatmospheric pressures.

References Cited in the file of this patent UNITED STATES PATENTS 2,071,253 Cal-others Feb. 16, 1937 2,130,989 Schemmelschmidt Sept. 20, 1938 2,252,555 Carothers Aug. 12, 1941 2,662,915 Loutz Dec. 15, 1953 FOREIGN PATENTS 82,441 Germany July 10, 1895 844,349 Germany July 21, 1952 OTHER REFERENCES Feiser et al.: Organic Chemistry, 2nd edition (1950), pp. 580-81 and 634.

Barkdoll et a1.: Chem. Abstracts, vol. 48 (1954), p. 2618.

UNITED STATES PATENT OFFICE @ETTFICATE 0F CQRRECTION Patent No., 2,894,025 July '7, 1959 Arthur William Anderson et al It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 2, line 8, equation right hand portion of the formula, for

COOH CH COOH read OOCH CH COOH column 5, claim 1, second formula, lower portion of the benzene ring, for

CH CH read 1 NH Signed and sealed this lst day of December 1959.,

(SEAL) Attcst:

KARL Hn AXLINE ROBERT C. WATSON Attesting ()fficer Commissioner of Patents 

1. A MONOMER HAVING THE STRUCTURAL FORMULA: 